Historical Rules · 22 April 2021
Rule 901.11a
Official source text from the 22 April 2021 Rules release
A player may planeswalk as the result of the “planeswalking ability” (see rule 901.8), because the owner of a face-up plane card or phenomenon card leaves the game (see rule 901.10), or because a phenomenon’s triggered ability leaves the stack (see rule 704.6f). Abilities may also instruct a player to planeswalk.